'All the time," Edele Lynch says, rolling her eyes as she settles herself on the sofa with a cup of herbal tea. "It's mostly 'Oh-ohhhh!', or 'I fight like me da', or sometimes 'What are ya like?'. All. The. Time."

“It’s true,” concurs her bandmate Sinéad O’Carroll. “Even in the taxi on the way over here, we had to correct the driver. He was saying ‘Na na na na’, instead of ‘Oh-ohhh!’. We’ll be having it shouted at us by taxi drivers when we’re 70.’”

At this point in their lives, the members of B*witched are resigned to being stalked by the spectre of their debut single, C'est la Vie , still irritatingly catchy 15 years after its release. They may have had four number one UK singles, a debut that went platinum on both sides of the Atlantic and US tours with the likes of N'Sync, but it's just as well that they've made peace with that first song – because now they're going to be hearing those chirpy catchphrases even more regularly than usual.

It's all down to The Big Reunion , the ITV2 documentary series that persuaded a number of 1990s pop acts (5ive, 911, Honeyz, Atomic Kitten and Liberty X were also featured) to bury their various hatchets and rekindle their pop magic. The documentaries were so popular that the planned one-off concert at the end of the series soon turned into a tour, which Blue have also joined. Today, half of B*witched are sitting in Dublin's Gibson Hotel, in the shadow of the O2, where next week they'll play their first Irish gig in more than 10 years .

“When we were first approached by the producers, I was like, ‘No way’,” says Lynch, the likeable lead singer with the bonecrushing handshake and the no-nonsense demeanour. “I just thought ‘I have a daughter in school, and it’s reality TV’. . . you just don’t know how it’s going to be edited. And when people have an opinion of you, that goes into the schoolyard. My little sister got a hard time with me being in B*witched and Shane being in Boyzone when she was still at school, so I didn’t know if I wanted that, or not. But my mind was changed when they started talking about doing it without me. I thought, ‘Well, I’m going to get the same amount of attention not being there, ’cos I was the lead singer’, so in the end I just said ‘fine, I’ll do it’. They bullied me!”

“I was different; to be honest, I said yes straight away,” admits O’Carroll. “I wasn’t too keen about the whole ‘reality TV’ aspect of it, but I thought more about what could come out of it. I was willing to take the risk to see if we could do a tour.”

The risk proved worthwhile when the show was a hit, yet getting back together after a 10-year split also meant re-treading rocky ground. Sony dropped the group just as they were preparing to record their third album, and O'Carroll's subsequent decision to leave the group (Lynch described it as "like my wife leaving me") spelled the end. The pair stopped talking altogether several years later – until this process brought them back together.

Today, there’s no sign of a division as the pair chatter like bosom buddies and subconsciously touch each other as they reference their estrangement.

"It was so stupid," says Lynch, shaking her head. "I always thought that it needed to be talked through to understand what actually happened, to fix it properly, but actually, what we needed was just to be in each other's space and understand what a new chemistry and new relationship this was. We didn't need to talk about anything, really. Without The Big Reunion , we wouldn't have had the opportunity to do that, because we'd fallen out. But it's been really good. I'm delighted that we've done it for that reason alone."

Lynch’s twin sister Keavy also struggled with depression towards the end of the band’s lifespan, but she has recuperated and is now training to be a counsellor herself, revived pop career aside.

There’s no getting away from the fact, however, that B*witched’s image was one of carefree bubblegum pop, a ‘double denim’ dress code and youthful fun. The Lynch twins were 19 when the group formed; today, the eldest member, O’Carroll, is about to turn 40.

"We're not young anymore? Is that what you're saying?" jokes Lynch. "But it was weird singing those songs again, yeah. I think even in the '90s line up on The Big Reunion , our songs are the youngest, by far, and we're probably the band whose image fits our songs the least, now; the others can still get away with it. Apart from Blame it on the Weatherman ; you could actually re-record that and release it now. Not that the others aren't good, but you kind of need a 17-year-old singing them. It's as well that we still look young, because if we didn't, I don't know what we'd have done. Sometimes you get these pop reunions, and it's 30 years later and they just look ridiculous. We get away with it. Somehow."

"It is hard, though," admits O'Carroll. "Especially C'est la Vie – because we're doing all the routines now in heels, and we're trying to not be as bouncy, trying to be a bit cool. But then again, we were never cool . . ."

After the split, O'Carroll kept her hand in showbiz by opening up a stage school for children, while Lindsay Armaou has dabbled in music and acting. Lynch and her sister Keavy formed another band, Barbarellas, but their 2011 album didn't quite take off. Lynch also spent time writing with the Xenomania team, an experience she describes as "amazing, but exhausting". Working with such world-class pop songwriters may yet stand to her if B*witched decide to record new material, something they are seriously considering.

“We’re definitely gonna go into the studio and see what happens,” says Lynch. “We were always thinking that we can’t pick up where we left off; it’s gotta be a new thing, so we’ve gotta get in the studio and see if the chemistry works. But it’d be silly not to, after doing all of this work and gelling together again. We’re worlds away from where we were, so I’d imagine lyrically, it’s going to be completely different. This time around, when we say ‘I’ll show you mine if you show me yours’, we might actually mean it.”

Given their chequered experience as pop stars, what would they do differently if they could do it all again?

“I’d probably try to enjoy it more,” says Lynch. “I spent a lot of time in bed, preparing for the next day – but so much so, that we actually missed a lot of the extras that went with it. We were always good at our job and always enjoyed it because of that, but in another way, it was all about work. And when we got to the end of it, we thought ‘Oh shit – we never socialised, not even with each other.’ We had no time for our friendship. I’ve been to Paris so many times, and I’ve never seen the Eiffel Tower. It’s terrible.”

“We didn’t actually stop to savour it,” agrees O’Carroll, reaching for a chocolate chip cookie to dip in her tea.

“We’re going on tour next week – you should be ordering salad!” exclaims Lynch in mock-horror.

"Ah, you have to live," says O'Carroll, laughing. C'est la vie , indeed.